Origin of Species Variorum

a nearly uniform, though perhaps extremely slight degree, and as they would be found embedded in slightly different sub-stages of the same formation, they would, according to the principles followed by many palæontologists, be ranked as new and distinct species.

If then there be some degree of truth in these remarks, we have no right to expect to find, in our geological formations, an infinite number of those fine transitional forms which, on my theory, .. have connected all the past and present species of the same group into one long and branching chain of life. We ought only to look for a few links, and such assuredly we do find— some more distantly, some more closely, related to each other; and these links, let them be ever so close, if found in different stages of the same formation, would, by many palæontologists, be ranked as distinct species. But I do not pretend that I should ever have suspected how poor a record of the mutations of life the best preserved geological section would present, had not the difficulty of our not discovering innumerable transitional links between the species which appeared at the commencement and close of each formation, pressed so hardly on my theory.

On the sudden Appearance of whole Groups of allied Species .

The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several palæontologists— for instance, by Agassiz, Pictet, and Sedgwick— as a fatal objection to the belief in the transmutation of species. If numerous species, belonging to the same genera or families, have really started into life .. at once, the fact would be fatal to the theory of descent with slow modification through natural selection. For the development of a group